The invention relates to the treatment of cardiac arrhythmia and more specifically treatment of cardiac arrhythmia by tissue ablation.
Tachycardia is a type of cardiac arrhythmia and is a serious, oftentimes, fatal condition characterized by rapid, uncontrolled, and ineffective beating of the heart. Most tachycardia falls into one of two broad categories: ventricular tachycardia (hereinafter VT) and supraventricular tachycardia (hereinafter SVT). VT occurs in the lower chambers of the heart, the ventricles, and frequently leads to serious complications, including sudden cardiac death. Atrial fibrillation and flutter, forms of SVT, originate in the upper chambers of the heart, the atria, and often result in chest pain, fatigue and dizziness and, while generally not life-threatening, is a leading cause of stroke in the United States.
Currently, many cases of VT and SVT are treated by drugs that modify the electrical characteristics of the heart tissue. However, the drugs do not eliminate or may not completely control the arrhythmia. In many cases of sustained VT, implantable cardiac defibrillators are used which deliver powerful shocks to the heart when fibrillation is detected. Concurrent treatment with drugs is standard therapy and each implantation of a cardiac defibrillator, of which there may be more than one per patient, is very expensive.
Some forms of SVT are treated by endocardial ablation, a minimally invasive procedure. During endocardial ablation, a mapping catheter is passed through an artery or vein into the patient""heart to find the site(s) of the arrhythmogenic tissue, the tissue from which the tachycardia originates. This same catheter or a separate catheter is used to transmit sufficient energy to thermally damage the tissue either by heating or cooling.
In atrial fibrillation the regular pumping action of the atria is replaced by a disorganized, ineffective quivering caused by chaotic conduction of electrical signals through the upper chambers of the heart. Although not immediately life threatening, atrial fibrillation may cause up to a 30% reduction in cardiac output and can lead to more serious conditions, including the formation of blood clots in the atria that can dislodge and travel to the brain resulting in stroke. Currently, the only curative treatment for atrial fibrillation is the surgical xe2x80x9cmaze procedurexe2x80x9d, an open heart procedure in which the surgeon makes several incisions in the right and left atria creating scar tissue to electrically separate portions of the atria. Despite clinical success of the maze procedure, it is time-consuming and demanding. The procedure requires open-heart surgery and is very expensive. Accordingly, only a modest number of maze procedures are performed annually in a limited number of centers.
The present invention provides an apparatus and method for treating cardiac arrhythmia that may be widely applicable, generally, to ablation of tissues of other body systems, such as urogenital or gastrointestinal.
In one aspect of the invention, a gripper tissue ablator device includes at least one gripper arm, a tissue contacting surface, at least one ablation element, and a handle. The tissue contacting surface on the gripper arm contacts or nearly contacts the tissue surface. The tissue contacting surface of the gripper arm causes the tissue to xe2x80x9ctentxe2x80x9d or fold, drawing the folded tissue into contact with the ablation element. In a preferred embodiment, the gripper tissue ablator device is applied to cardiac tissue, such as the epicardial surface of the atrium, to ablate tissue. In other embodiments, the gripper tissue ablator device of the invention is applied to other tissue such as tissues of the urogenital tract, gastrointestinal system, or skin to ablate the tissue.
In yet another aspect, the invention relates to a method for ablating tissue. In one embodiment of this aspect of the invention, the gripper tissue ablator device is used to ablate tissue, preferably atrial tissue. In this embodiment, the epicardial surface of the heart is approached via a thoracotomy or thoracoscopy. The operator grasps the handle of the device and applies the ablation member on to the atrial tissue site to be ablated. Following the application of negative pressure to the tissue generated by a pump or syringe in communication with surface gripping elements, the device is moved in a direction substantially perpendicular to the tissue plane, pulling the tissue underlying the gripping elements in the same direction. By pulling the tissue underlying the gripping elements, the tissue xe2x80x9ctentsxe2x80x9d by forming a fold or crease in the tissue in contact with the ablation member. As the tissue folds, the endocardial surface at the sides of the fold are drawn together. In one embodiment, the tissue is pulled upward into the ablation device, which applies ablation energy to the tissue that is xe2x80x9ctented.xe2x80x9dAblation energy to heat, freeze, or otherwise kill tissue, such as a cryogen, is applied to the ablation elements adjacent to the gripping elements on the tissue contacting surface of the ablation member to cause one or more myocardial ablative lesions.
In another embodiment of the method of the invention, a gripper tissue ablator device having more than one gripper arm is used. In this method of the invention, the operator approaches the tissue surface in the same manner as described above. The handle of the device is grasped by the operator and the gripper arms are applied to the surface of the epicardium. The tissue contacting surface of the gripper arms holds fast the tissue in contact with the tissue contacting surface by adhesion, friction, or suction. The gripper arms are moved toward one another to cause the tissue between the arms to tent. Alternatively, the ablation member is made from a flexible material. The operator grasps the ablation member and squeezes the ablation member to cause the tissue gripped by the ablation member to fold. The tissue in the fold is ablated by application of ablation energy, such as a radio-frequency energy to ablation elements disposed on the gripper arms, on the ablation member, or on both the ablation member and gripper arms.